18. Our friends ______ (have) a lovely new house in the country and they ______ (have) a house-warming party this Sunday.

Для обладания домом используется Present Simple: have. Для запланированного события в ближайшем будущем — Present Continuous: are having.

Our friends have a lovely new house in the country and they are having a house-warming party this Sunday.

Ответ: have; are having